Gasification Feed System Methanol Removal via Recycled CO2
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Solution Overview
Problem
Current dry-coal feed systems using CO2 as an inert gas for pressurization face challenges with methanol contamination exceeding allowable vent levels, leading to environmental regulation issues and increased costs due to the need for expensive absorbers that absorb water, making it difficult to find acceptable alternative technologies.
Innovation Solution
A process where recycled CO2 is introduced into a sluice vessel at a reduced flow rate to pressurize the vessel, allowing the carbonaceous feed to absorb methanol effectively, with elevated temperature and pressure aiding in reducing methanol content before venting, thus optimizing absorption without additional equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CO2 is used for pressurization in the sluice vessel, then the coal feed can be transported to the gasifier, but the vented CO2 contains excessive methanol (300-400 ppm) exceeding environmental regulations
Solution Approach 1:
The patent converts the harmful effect of CO2 containing methanol by using the CO2 stream itself as the absorption medium. The CO2 is passed through the coal feed in the sluice vessel, and the coal absorbs the methanol from the CO2 stream. This transforms the harmful CO2 stream into a beneficial absorption medium that simultaneously pressurizes the vessel and removes methanol.
Solution Approach 2:
The coal feed acts as an intermediary substance between the CO2 stream and the environment. The coal absorbs methanol from the CO2, serving as a mediator that transfers methanol from the gas phase to the solid phase, thereby purifying the CO2 before venting.
2Object-affected harmful factors
If expensive absorbers are installed to remove methanol from CO2, then environmental regulations can be met, but plant costs increase significantly
Solution Approach 1:
The system uses itself to solve the problem. The coal feed, which is already present in the sluice vessel for its intended purpose, is utilized to absorb methanol from the CO2 stream. This self-service approach eliminates the need for separate, expensive absorption equipment while meeting environmental requirements.
Solution Approach 2:
The coal feed performs multiple functions: it serves as the carbonaceous material to be gasified, and simultaneously acts as an absorption medium for methanol removal. This multi-functionality eliminates the need for dedicated methanol removal equipment, reducing plant complexity and cost.
3Object-affected harmful factors
If water-based absorbers are used to remove methanol from CO2, then methanol can be absorbed, but the CO2 becomes contaminated with water making it unsuitable for dry coal feeding
Solution Approach 1:
The patent uses a homogeneous solid-phase absorption system where coal (a dry solid) absorbs methanol from the gas phase. This maintains the dryness of the CO2 stream while removing methanol, unlike water-based liquid absorption which would introduce moisture contamination.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces methanol content in the vented CO2 to acceptable levels, adhering to environmental regulations while minimizing costs by utilizing existing CO2 recycling and avoiding the need for expensive absorbers.
Implementation Method 1
The CO2 that is used in this process may be derived from a Rectisol syngas treating plant... the recycled CO2 may contain methanol up to a concentration which exceeds allowable vent levels... introducing at least recycled CO2 into the sluice vessel via one or more gas inlets covered by the solid carbonaceous feed, to pressurize the sluice vessel
Data Source
AI summary
A process for the gasification of a solid carbonaceous feed, the process comprising the steps of: introducing a batch of the solid carbonaceous feed into a sluice vessel, while an internal pressure in the sluice vessel is at a first pressure; introducing at least recycled CO2 into the sluice vessel via one or more gas inlets covered by the solid carbonaceous feed, to pressurize the sluice vessel from the first pressure to a second pressure exceeding the first pressure, during a predetermined time period; closing the one or more gas inlets; opening a feed outlet of the sluice vessel to supply the batch of the solid carbonaceous feed to a feed vessel for feeding the solid carbonaceous feed to a gasification reactor; closing the feed outlet; venting the sluice vessel to reduce the internal pressure to the first pressure; and repeating the process.